And no this is not a piece of software you download. But a set of terminal commands you use to disable My SQL. Which is actually preventing the machine from shutting down correctly. See the latest version of my SQL actually doesn't like Sierra at all and prevents the machine from shutting down by causing a loop in the wifi adapters drivers which honestly creates loads of issues.

2. the o.s runs extremely slow

True Mac OS X Sierra runs really slow in fact a lot of users have reported that Mac OS X Sierra continues to write to the hard drive 24/7 causing lag and even worse beachballs of death or beachballs of freezing.

Solution wait for the 10.12.01 update it should fix these issues.

3. I would like to go back to my older o.s but the machine refuses to boot the installer.

Reset your SMC this should fix the boot device not found error.

4. I want to install Sierra but can't because apple decided to be jerks and remove my expensive machine from there list of supported machines can I still run the o.s

Actually yes but due to the legality of such a program I can only tell you its called the Sierra patcher it is created by dosdude.

No I can't tell you where to get it and yes it does work on unsupported Macintosh computers because the drivers are still there for the 2009 Mac mini Mac Pro and even MacBook Pro apple just decided to rig the o.s again to force users into a more expensive machine.